The prior art discloses a wide variety of diphosphate flame retardant compounds which contain two phosphate groups (often containing two phenyl substituents each) linked together by a bridging group --O--R--O--, where R comprises an arylene or alkylene group. Certain disclosures exist which include cyclohexylene as a possible alkylene group for R, including U.S. Pat. No. 3,869,526 to M. Combey et al. (see Col. 1, line 27) and U.S. Pat. No. 4,343,732 to T. Zama et al. (see Col. 3, lines 52-53).